Development apparatus for electrophotographic copies

ABSTRACT

An apparatus for liquid developing of electrophotographic copies has a passage for the copies through the liquid in the reservoir, said passage being bordered on one side by a hollow rotating cylinder having internal blades for pumping the liquid through openings in the cylinder into said passage.

[ July 4,1972

United States Patent Dols [54] DEVELOPMENT APPARATUS FOR 6542 792 l l 55 99 0 wo 1 .1

ELECTROPHOTOGRAPHIC COPIES Huebner Limberger...... 3,186,326 6/1965 Schmidt.............

[72] Inventor: Wilhelmus Emilius Maria D018, Venlo, 3 245 341 19 Childress ct Netherlands 3,388,688 6/1968 Stanton..............

3,547,076 12/1970 Saklikar.........

OTHER PUBLICATIONS Tech. Disclosure by T. M. Crawford, Vol. 8, No. 4, S

[73] Assignee: Van Der Grinten N.V., Venlo, Netherlands [22] Filed: June 18, 1970 eptember 65, IBM Tech. Disclosure Bulletin Title: Developing Electrostatic Charge Patters [21] Appl. No.: 47,524

[30] Foreign Application Priority Data June 24, 1969 Netherlands.........................

.6909655 Primary Examiner-Mervin Stein Assistant Examiner-Leo Millstein AttorneyAlbert C. Johnston .118/637, 95/93, 118/424, 118/427, 118/DIG. 23, 117/37 LE mm m .wnmFm i wm ruy qb on t .l o dD. h m w nD. "m or. c o e f mfi T md C .9 m .m W m D. a T wmm C 2. Vent A .mmwm mmen uf 0 3 U a r. m Pe wdm m aa m .16 Pwom h 1. 1 a e 7 m 5 uo I Apfr. mum n 5 N6, m G9 15 M MLL "77 m m 7 w "3 "6 h my C 1 s l u. c mm H mm r. "a h "n e I n "r m m d M MF 1.] 1 18 6 55 5 [.1 I.

through openings in the cylinder into said p assage.

UNITED STATES PATENTS 2,267,877 12/1941 Sebell 4 Claims, 4 Drawing Figures PATENTED JUL 41972 IN VENTOR WILHELMUS EM. DOLS Mun.

ATTORNEY DEVELOPMENT APPARATUS FOR ELECTROPHOTOGRAPHIC COPIES This invention relates to an apparatus for developing electrophotographic copies with the aid of a liquid, of a kind which is provided with a liquid reservoir, a passage through said reservoir for submerging and passing copies to be developed therethrough, a developing electrode positioned below the level of the liquid and being curved and provided with openings, the convex side of said electrode bordering the such passage to one side, said apparatus being further provided with means for displacing the liquid in order to urge developing liquid from the concave side of the developing electrode through the said openings.

Apparatus of this kind is known, for instance from [1.8. Pat. No. 3,245,330 and from Dutch patent application 67,02972. In such known apparatus the developing liquid is circulated by a pump so that the liquid is pressed from a distributing tube through openings in the developing electrode and is thus sprayed onto and into contact with the copies to be developed, which pass the electrode. The pressure exerted by the liquid keeps the passing copy material free from contact with the electrode and pushes it against guide means forming the opposite side of the passage and positioned at a short distance from said electrode. Thus direct contact between the copy material and the electrode, which could harm the formation of the image, is prevented Moreover, the copy material is always at a short distance from the electrode, which is favorable for the operation of said electrode. The circulation of the liquid also assures that the liquid layer in contact with the copy material always contains a sufficient quantity of color particles notwithstanding the fact that color particles are deposited from said liquid onto the copy material.

Such known devices are rather complicated, for instance by the necessary duct system etc. and by the fact that they have to be provided with a powerful pump (for instance having a capacity of 6 liters per minute) in order to obtain correctly developed copies at relatively low speeds of passage of the copy material (for instance of m per minute), so that copies having dark image parts and a clear background are obtained without objectionable edge effects.

The purpose of the present invention is to provide an apparatus of the kind outlined above which is simpler in structure and which gives good results even at very high speeds of passage of the copy material (for instance of 30 m per minute).

According to the invention, in an apparatus of that kind the developing electrode is constituted by the peripheral wall, or jacket, a hollow rotating cylinder and the liquid displacement means consist of blades rigidly connected to the concave side of the jacket. It results that by rotation of the developing electrode at a low energy consumption a very intensive and uniform flow of developing liquid through the passage and along the copy material passing therethrough is obtained. The blades press the liquid forcibly through the openings in the electrode so that contact betweenthe copy material and the electrode is prevented. The direction of rotation of the electrode may be opposite to the direction of movement of the copy material, but it is also possible to have these directions the same, in which case the electrode should rotate at a speed which at the periphery is higher than the speed of passage of the copy material. It is easy to determine by experiment what the rotational speed of the electrode should be, depending upon the diameter of the electrode cylinder, the number and size of openings therein and the pattern in which such openings are provided in the electrode, the shape of the blades, etc.

It is known in developing apparatus for electro-photographic copies to provide an impeller below the level of the liquid, for instance as shown in US. Pat. No. 3.388.688, or to pump the liquid by force in the longitudinal direction through the passage, as is shown in U.S. Pat. No. 3,377,988.

The following may serve to further explain the invention. The developing liquid is electrically insulating and contains electrostatically charged color particles in dispersion. The developing electrode serves, as known, for suppressing the edge effect for image parts of larger area and increases, also for thin image lines, the electric field strength of the electric charge image. The circulation of the liquid particularly serves for refreshing the liquid zone in contact with the copies, so that always a sufficient quantity of color particles is applied to said zone notwithstanding the fact that color particles are deposited from this zone upon the copies.

The invention will now be explained in further detail by way of example with reference to the accompanying drawing.

IN THIS DRAWING FIG. 1 is a diagrammatic vertical section through an apparatus according to this invention;

FIGS. 2 and 3 are perspective views of end parts of develop ing electrodes according to the invention, in two difi'erent embodiments; and

FIG. 4 is a diagrammatic section perpendicular to the axis of the electrode according to FIG. 3.

In FIG. 1 reference numeral 1 indicates a liquid reservoir filled with developing liquid to level 2. The copy material to be developed is guided through this bath along a path indicated by arrows, with the aid of rollers 3 and 4 feeding the copies to the bath. The copies are supported in and guided through the bath by the guide wires, strips or the like, indicated by 7 and thereafter are discharged with the aid of the rollers 8 and 9 which also press a superfluous quantity of liquid from the copy material so that this liquid falls back into the bath.

In the space within the guide means 7 a developing electrode is positioned which is formed by a hollow metal cylinder 10 provided with a large number of openings 11. Within the jacket of said cylinder 10 there are blades 12 which at their outer ends are connected to said jacket and at their inner ends are connected to a shaft 13 which is rotatably supported by means (not shown) in the walls of the reservoir 1. Thus the jacket, the blades 12 and the shaft 13 of the cylinder form an integral structure. Shaft 13 is, in a manner not shown, connected to drive means so that the electrode can be rotated thereby.

Upon rotation of the electrode the blades 12 displace the liquid present within the cylinder 10 so that this liquid is pressed out through the openings 11. Thereby in the passage between the guide means 7 and the cylinder 10 a forceful and uniform flow of liquid is obtained, which moves over the image side of the copy material being passed therethrough. The impulse of this flow presses the copy material against and into contact with the guide means 7, so that direct contact between the image side of the copy material and the electrode is avoided, and nevertheless said image side is always very close to said electrode (for instance at a distance of 0.5 to 1 mm), so that the developing electrode is allowed to operate very effectively. In order to prevent the openings in the electrode from causing irregular degrees of development of the copies, the electrode is rotated at a much higher speed than the linear speed of the copy material; for instance, the peripheral speed of the electrode is 4 to 10 times higher than the linear speed of the copy material; or the electrode can be driven in a direction opposite to the direction of movement of the copy material.

The liquid being discharged from the rotating electrode 10 outside the developing zone is captured by a shield 14, which prevents the copy material entering the device from being pushed too much against the guide means 7 or being pushed away at its front edge so far to the left in FIG. 1 that it will not reach the guide means 7 in the correct position. Part 15 of shield 14 together with guide means 7 forms a passage for the copy material moving out of the bath in the direction of the rollers 8 and 9.

By the operation of the blades 12 the liquid in the reservoir is circulated forcefully, and through the open end faces of cylinder 10 fresh liquid is allowed to enter easily into the electrode. One end of such an electrode is shown in FIG. 2.

Instead of such an open end electrode, it is possible to use on electrodes as shown in FIGS. 3 and 4, in which the electrode cylinder has closures on its ends and is provided with a hollow shaft provided with openings within the cylinder between the blades with openings, said hollow shaft being, by suitable means not shown, in communication with the main quantity of liquid in the reservoir 1, e.g., by making the reservoir 1 larger than the cylinder in the direction of the axis of the cylinder and providing the shaft with suitable openings in the reservoir outside the cylinder. As seen in FIGS. 3 and 4, covers 16 close the ends of the cylinder a and there is a hollow shaft 17 which between the blades 12a is provided with openings 18. In particular when the electrode rotates at high speeds (for instance of 200 revolutions per minute) such a structure gives a very good pumping action.

Instead of discrete perforations, e.g., of circular sha e, as indicated in FIG. 1, the electrode may be provided with longitudinal slot-like openings 19 in the jacket as shown in FIG. 2.

In an attractive and advantageous embodiment of an electrode according to this invention a jacket is formed as shown in FIGS. 3 and 4 by arcuate outer end parts of blades 12a and the openings in the jacket are slots 19a, left open between the tenninal edges of said end parts and the adjacent blades.

The electrode may be built up in different ways. It can consist of sheet metal parts connected mutually by welding, brazing, soldering or similar means (FIG. 1). It is also possible to make the electrode as a single body (FIG. 4), for instance from an extruded profile. It is also possible to build up the electrode of FIG. 4 from eight extruded profiles, each including as a U-shaped body one blade, one arcuate inner leg and one arcuate outer leg, which profiles are connected together while leaving open slots 18 and 19 between free edges of their respective legs and the respective blade portions of adjacent profiles.

I claim:

1. An apparatus for liquid developing of electrophotographic copies, provided with a liquid reservoir, a passageway through said reservoir for submerging and passing copies to be developed therethrough, a developing electrode positioned in said reservoir below the level of the liquid and being curved and provided with openings, the convex side of said electrode bordering the said passageway at one side thereof, said apparatus being provided with liquid displacing means which press the developing liquid from the concave side of the developing electrode through the said openings, characterized in that said developing electrode is the peripheral wall of a hollow rotating cylinder and said liquid displacing means include blades disposed inside and at an angle to the concave side of said wall.

2. An apparatus according to claim 1, said wall being formed by arcuate outer end portions of said blades and said openings being slots provided between free terminal edges of said end portions and the adjacent blades.

3. An apparatus according to claim 2, said cylinder being built up of extruded profile sections in a number equal to the number of said blades and slots, each profile section being substantially U-shaped and comprising a central part forming a blade, an inner leg forming a shaft part and an outer leg forming part of said peripheral wall, there being a slot between a free edge of each leg of each profile section and the central part of an adjacent profile section.

4. An apparatus according to claim 1, said electrode cylinder having closures on its ends and having a hollow shaft passing through at least one of said closures, said blades being connected to said shaft, and said shaft being provided with openings therethrough in regions thereof between said blades, at least one end of said shaft protruding outside the electrode cylinder and opening into the liquid containing space of said reservoir for communication with the liquid therein.

IR l l 

1. An apparatus for liquid developing of electrophotographic copies, provided with a liquid reservoir, a passageway through said reservoir for submerging and passing copies to be developed therethrough, a developing electrode positioned in said reservoir below the level of the liquid and being curved and provided with openings, the convex side of said electrode bordering the said passageway at one side thereoF, said apparatus being provided with liquid displacing means which press the developing liquid from the concave side of the developing electrode through the said openings, characterized in that said developing electrode is the peripheral wall of a hollow rotating cylinder and said liquid displacing means include blades disposed inside and at an angle to the concave side of said wall.
 2. An apparatus according to claim 1, said wall being formed by arcuate outer end portions of said blades and said openings being slots provided between free terminal edges of said end portions and the adjacent blades.
 3. An apparatus according to claim 2, said cylinder being built up of extruded profile sections in a number equal to the number of said blades and slots, each profile section being substantially U-shaped and comprising a central part forming a blade, an inner leg forming a shaft part and an outer leg forming part of said peripheral wall, there being a slot between a free edge of each leg of each profile section and the central part of an adjacent profile section.
 4. An apparatus according to claim 1, said electrode cylinder having closures on its ends and having a hollow shaft passing through at least one of said closures, said blades being connected to said shaft, and said shaft being provided with openings therethrough in regions thereof between said blades, at least one end of said shaft protruding outside the electrode cylinder and opening into the liquid containing space of said reservoir for communication with the liquid therein. 